Method of manufacturing stereotype mats



June 17, 1941. DAVENPORT 2,245,555

METHOD OF MANUFACTURING STEREOTYPE MATS Filed Jan. 8, 1938 FRANKLYN E. DAVENPORT INVENTOIL ATTORNEY.

Patented June 17, 1941 METHOD OF MANUFACTURING STEREd- TYPE MATS Franklyn E. Davenport, Watertown, N. Y., p signor to Knowlton Brothers, a corporationfof v New York Application January 8, 1938, Serial No. 184.1 13

3 Claims.

This invention relates to improvements in stereotype mats and their manufacture, and particularly pertains to what is known in the art as dry mats as distinct from so-called wet mats. They are also sometimes referred to as matrices" or flongs."

Stereotype mats of the so-called dry mat 1 type are ordinarily a fibrous sheet construction felted to any desired thickness from a suitable pulp stock, such as chemical wood pulp, and some filling material on a wet machine or press roll. After a sheet is built up to the required thickness and given certain treatments, such as coating, calendering, control of moisture content, it is cut up into commercial sizes for being made into stereotype mats.

A form containing the type is first set up with a stereotype mat superimposed thereon and covered with blankets or felts. The type is then compressed against the mat to impress thereon a reverse impression of the type. The type impressed mat is dried to retain permanently the type impression. Thereafter it is placed in a v casting machine, and molten stereotype metal is poured into the casting machine to mold a metal stereotype fiat or cylindrical plate having on its surface a duplicate of the original type which has been impressed upon the mat. These plates are made flat for use on flat or bed presses, and cylindrical for use on rolls of a cylindrical press. The stereotype plates or cylinders are used on the printing press.

Dry mats are usually from 0.028 to 0.036 'of an inch in thickness, and vary in hardness accord? ing to requirements. Although known as dry mats, they are not used in a dry condition free from moisture. Unlike wet mats, hereinafter briefly described, a supply of them can be made up and kept in a dry condition by the printer if he manufactures his own mats; Ordinarily, however, tion by theprinter. few companies in the expensive. Many are imported. Before being suitable for use, they need to'be moistened to provide a moisture content from about ten (10%) to thirty (30%) per cent. This is ordinarily done by placing the mats-in a humidor. They are then, when having the proper moisture content, compressed by the type. form, as above described. ,A high degree of pressure is required and often the face of the type form is destroyed before a sufiicient number of stereotype mats can be formed. A 'mat should be serviceable for making at times not less than twenty casts. The

They are made by only a type impression having been given to the mats by the type form, the mats are removedv and placed in a so-called scorcher for drying out the moisture in a short time. They are then ready for use in casting the molten metal type.

Wet mats" comprise several relatively thin sheets, usually two or three, of blottingpaper and several sheets, about four, of tissue paper glued together by a suitable adhesive; such as starch, dextrin or the like. The tissue sheets are employed as facing layers for the blotting paper sheets, particularly on the face against which the type form is pressed in order to obtain a well defined and smooth impression with no project-'- ing loose fl ber ends or loose fibers. The wet mat, after being constructed, is kept in a wet condition until used and then must be dried on the type form to prevent shrinking and warping thereof. Besides taking much time, their manufacture involves much labor and skill for pro,- ducing satisfactory construction.

While the dry mats can be more quickly made and are more conveniently handled than the wet mats, they have -a rougher surface and therefore do not give as sharp and distinct impressions, particularly as to half tones. They do not have the plasticity of the wetmats and are frequently, fractured during the molding process, thereby permitting the metal to flow into the fractures or fissures. This, of course, tears the face of the mats when the casting'is removed and renders them unfit for further casts. Frequently the molten metal flows into the surface interstices between the fibersand tears the fibers loose or loosens their ends, causing the surface to be rough and imperfect.

To overcome the latter objections, it has been proposed to employ very finely divided fibers" and mix filling material in the pulp stock to they are purchased in this dry condicountry and are relatively provide as smooth 9. surface as possible on the mat. While these improvements do provide better mats, they do not overcome the need for moistening the mats with the proper moisture content to condition them for'use. 1 The aim of the present invention is to provide improved mats which do not require moistening 'with a moisture content previous to their use,

but are so constructed that they are suitable for use without any preliminary treatment by the printer, are sufficiently flexible, are of a con-' struction to e impressed with the type form in sharp and smooth definitions, and have the fibers fully protected without danger of loosening them or their ends. v

Generally described, the invention comprises with the thermoplastic a foundation sheet of rial, such as a paper, either of single or multiple ply, having a thermoplastic composition associated with the foundation that is adapted to melt under heat and pressure, and flow to impregnate the fibrous foundation. when the mat is cooled, the impregnated material solidifies and hardens the mat into a strong, hard, non-brittle condition material reinforced by any suitable flexible mate the fibrous foundation.

For a better understanding of the invention, reference may be made to the drawing in which:

Fig. 1 is a cross-sectional view of a portion of a dry mat embody the invention; and

Fig. 2 is a cross-sectionalview of the type impressed mat. Referring to the drawing in which like numerals are used to designate like parts, numeral l is a foundation sheet of any suitable material sufliciently absorbent to be impregnated with a thermoplastic material. A paper or felt sheet of chemical wood pulp has been found suitable, and is formed on a wet machine or press roll, or conventional type of cylinder or Fourdrinier paper machine, to the desired thickness. The foundationmay be a single or multiple construction.

Thermoplastic material, having a relatively high melting point and adapted to soften and flow at elevated temperatures, but being sufficiently hard and tough to withstand deformation at normal temperature, is associated with the foundation. It may be incorporated in a finely divided granular form in the foundation sheet or may be applied as a coating 2 to one side thereof or both sides of the foundation. Or if the sheet be a multiple one, the thermoplastic material may be an intermediate layer between two or more plies. Synthetic and natural resins or other materials of this character, such as copal, dammar, sandarac, oleo resins, hard native asphalts, asphaltites, wurtzlite asphalt and hard coal pitch, or a combination thereof, are suitable thermoplastic materials. Where the thermoplastic material is applied as a coating, it may advantageously be coated or covered with a thin protecting layer 3,

such as wax or the like.

The thermoplastic treated fibrous mat is placed felt, fabric, or the like,

in a hot press with the type form. In the embodiment shown the sheet is placed in the press with the coated side down and the type of the type form against the opposite or uncoated side. No felts or blankets need be inserted between the i type form and the mats as heretofore. With comunder heat a type comprising forming" providing normally paratively moderate pressure applied, the thermoplastic coating melts and flows upwardly to permeate and impregnate the absorbent fibrous foundation sheet and molds itself and the foundation into a form with the reverse impression of the type imparted thereto. The type impressed mat is then cooled intoa strong, which perfect type castings may be made.

While the invention has been described in detail and preferred embodiment has been illustrated for carrying it into efiect, there may be various changes in details of construction without departing from the spirit of the invention.

I claim:

1. The method of making a stereotype mat comprising forming an absorbent fibrous felted foundation, coating the face opposite the type engaging surface with a layer of normally hard and tough thermoplastic material, and compressing under heat a type form against the side opposite the coating layer, causing said thermoplastic material to impregnate the foundation and the impregnated foundation to be impressed with the type form.

2. The method of making a stereotype mat an absorbent fibrous felted foundation, coating the opposite faces of the foundation with-a layer of normally hard and tough thermoplastic material, and compressing form against one of the coated faces, causing said thermoplastic coatings to impregnate the foundation and the impregnated foundation to be impressed with the type form.

3. The method of making a stereotype mat comprising forming an absorbent foundation, hard and tough thermoplastic material in the foundation at an area remote from the type engaging surface, and compressing under heat and pressure a type form against the foundation, causing said thermoplastic material to impregnate the foundation and the impregnated foundation to be impressed with the type form.

FRANKLYN E. DAVENPORT.

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